Anyone who has ever made a relatively long flight aboard a commercial passenger jet is probably familiar with their toilets. Flushing these devices results in toilet fluids and solid wastes being drawn from a toilet bowl down a waste line. Unlike conventional toilets, where waste exits the toilet bowl via a circular water flow that carries the waste through a bottom outlet, the toilets in the most recent passenger jet models are vacuum toilets that rely upon suction for removing waste. This creates the familiar sucking sound that accompanies flushing this particular toilet. Older jets have recirculating systems where solid waste is essentially strained from toilet liquids, and the liquids are reused for later flushings.
The present invention relates to the more recent vacuum toilet systems. A common attribute of such systems is that a flushing airflow is created by venting toilets externally of the aircraft. This is accomplished by opening a valve, which creates an airflow path from a given toilet bowl to the outside or ambient atmosphere via a waste line and tank system. The pressure differential between the toilet cabin and the ambient is what actually generates the airflow At certain low elevations, where the pressure differential is not great (below 16,000 feet, for example), a vacuum blower is employed to assist or augment the natural pressure differential between inside and outside the aircraft.
Of course, the solid and liquid waste in the toilet is not simply dumped outside the aircraft. Instead, it is separated from the airflow, and deposited in a waste tank prior to venting the air overboard.
Typically, the airflow and entrained waste travel from the toilet to the waste tank via conventional pipes or lines. The conventional waste tank has one or more waste inlets configured to direct the flow circumferentially in a clockwise direction around the tank's interior, but at a level that is above and parallel to the level of waste already in the tank. As a result, a combination of centrifugal forces and gravity cause separation of much of the entrained matter from the airflow, and it simply drops downwardly into the tank. Some entrained matter remains with the airflow and is removed via a separator as it exits the tank. This device is normally positioned inside the top portion of the tank.
To function effectively, the conventional separator is dependent upon the above-described clockwise or circular airflow generated when it enters the tank. The conventional separator has inlets which face away from such direction, requiring the flow to first turn nearly 180.degree. in order to gain entry into the separator. This creates a sudden momentum change that helps separate heavier particles of solid waste and droplets of moisture in the flow prior to further processing inside the separator. A good example of this motion is illustrated in U.S. Pat. No. 4,385,912, issued to Parrick et al. on May 31, 1983. Such reference is illustrative of the operation of all separators presently used by The Boeing Company in its aircraft toilet systems.
The waste tank system described above has sensors for detecting the level of waste inside the tank. These sensors have faces that are positioned at a certain vertical height along the tank's inner wall, and provide an electrical signal indicating a full tank in response to contact with the waste as its level rises. In the full tank condition, the level sensors remove power from all toilets connected to that tank.
The above-described tank inlet arrangement, which creates a circular flow motion inside the tank, also creates a problem in that it tends to coat the waste level sensor faces with solid and liquid waste. This has been known to cause the sensors to emit signals falsely indicating a full tank, resulting in unnecessary shutdown of the toilet. This naturally results in a serious inconvenience for the passengers.
The typical waste tank system also has one or more rinse nozzles that protrude into the tank. These are connectable to an external source of clean water for periodically rinsing and/or cleaning the tank during aircraft maintenance intervals. They also tend to be coated by incoming waste from tank inlets which can clog them.
In addition to the coating and clogging problems just described, another problem associated with the conventional waste tank system is that its separator typically projects downwardly a significant distance into the tank. This consequently blocks or shadows portions of the tank's inner walls from the spray of the rinse nozzles, and has made it difficult to completely clean the tank, including coated sensor faces. It also decreases the maximum storable waste volume inside the tank since the separator itself takes up some of the space at the tank's top.
As will become apparent, the separator disclosed here provides an improved design for use in aircraft toilet systems that overcomes the above problems That is to say, a separator in accordance with the invention does not require creation of a circular airflow in one particular direction inside the tank, like the system described above. This enables more flexibility in arranging tank inlets in order to avoid coating sensors with waste matter. Further, a separator in accordance with the invention protrudes only slightly into the tank. This creates more space for waste, and eliminates the rinse blocking problem described above.